The present application relates to a structure-defining material for organic light-emitting devices (OLEDs). OLEDs use electro-luminescent organic materials, for example, to provide lighting elements for display devices. OLEDs may be designed to replace conventional non-organic display technologies or for new applications.
A typical OLED display device has a xe2x80x9csandwichxe2x80x9d or layered construction. To construct a typical OLED, first, a transparent conducting layer is deposited onto a transparent substrate. The transparent conducting layer typically comprises a transparent conducting oxide material, e.g., indium-tin oxide (ITO). Other materials, including thin metal films, alternatively may be used for the transparent conducting layer. The transparent conductive layer may serve as one of the electrode layers (typically the anode) of the OLED. Next, a set of one or more organic layers is deposited onto the transparent conducting layer. The depositing techniques used may depend on the types of organic material deposited. The organic layers may serve various functions such as hole injecting, hole transporting, electron injecting, electron transporting, and/or as emitting or intermediate layers. Finally, one or more conducting layers are deposited and may serve as another electrode layer (typically the cathode) of the OLED device. Typically, this second electrode layer has a sub-layer formed of a low work function metal (e.g., Ca, Mg, Ba or Li), and a capping sub-layer of a more air-stable high work-function metal (e.g. Ag or Al). Other types of material for the second electrode layer, such as metal alloys or combinations of insulating and metal sub-layers, may be used.
In operation, a voltage is applied across the electrode layers, charge carriers are injected into the organic layers, recombination takes place, and part of the recombination energy leaves the device as photons. The photons pass through the transparent first electrode layer and substrate and are visible as emitted light.
The present inventors recognized that using poly-siloxane as a structure-defining material for one or more separator or insulating structures in an OLED (e.g. a bank structure for pixel confinement, insulating strips for isolating electrodes, etc.) results in dramatic improvements in manufacturing yield, ease and cost, as well as improved reliability and lifetime of the OLED. Consequently, the present inventors developed OLEDs having poly-siloxane insulating structures and corresponding manufacturing techniques.
In one implementation, a light-emitting device may include a plurality of electrode layers, including an anode layer and a cathode layer, an electro-luminescent organic layer disposed between the anode and cathode layers, and a poly-siloxane insulating structure separating the electro-luminescent organic layer into a plurality of light-emitting elements. In addition, the light-emitting device may include at least one other organic layer disposed adjacent to the electro-luminescent organic layer. In that case, the at least one other organic layer may be configured to perform one or more of the following functions: hole injection, hole transportation, electron injection, and electron transportation The poly-siloxane insulating structure, which may separate the electro-luminescent layer into a plurality of pixels, may be a thin sheet of poly-siloxane material having a plurality of apertures. Each of the anode layer and cathode layer may include a plurality of electrode strips arranged such that anode layer electrode strips and the cathode layer electrode strips coincide at regions corresponding to apertures of the poly-siloxane insulating structure. The at least one electrode layer may be configured to independently address each aperture of the poly-siloxane insulating structure as a display pixel, and wherein the at least one electrode layer is further arranged in an active matrix configuration. The poly-siloxane insulating structure may form a bank structure that insulates the plurality of light-emitting elements from each other. The light emitting device further may include one or more insulating strips on the poly-siloxane insulating structure, wherein at least one insulating strip includes an overhanging portion or a base portion or both, either or both of which may be formed of poly-siloxane material in one or both of the overhanging portion and the base portion.
In another implementation, a method of constructing a light-emitting device may include forming a first electrode layer on a substrate, forming on the first electrode layer a poly-siloxane bank structure having apertures, depositing one or more organic layers into the apertures of the poly-siloxane bank structure, and forming a second electrode layer such that the one or more organic layers deposited into the apertures are disposed between the first and second electrode layers. Depositing one or more organic layers may include depositing an electro-luminescent organic layer. Alternatively, or in addition, depositing one or more organic layers may include depositing at least one other organic layer (e.g., a conductive polymer layer) disposed adjacent to the electro-luminescent organic layer. In that case, the at least one other organic layer may be an organic layer configured to perform one or more of the following functions: hole injection, hole transportation, electron injection, and electron transportation. The method further may include patterning the poly-siloxane bank structure to separate the light-emitting device into a plurality of pixels. Forming the poly-siloxane bank structure may include forming a thin sheet of poly-siloxane material having a plurality of apertures, each aperture corresponding to an individual light-emitting element. Each of the first electrode layer and the second layer may be formed as a plurality of electrode strips arranged such that the first electrode layer strips coincide with the second electrode layer strips at regions corresponding to the poly-siloxane bank structure""s apertures. Forming the first electrode layer further may include arranging the first electrode layer to independently address each aperture of the poly-siloxane bank structure. Arranging the first electrode layer further may include configuring the first electrode layer as an active matrix. Depositing the one or more organic layers may include one or more of spin-casting, dip-coating, screen printing, flexo printing, and ink-jet printing. The poly-siloxane bank structure may be formed before the one or more organic layers are deposited. Or one or more organic layers may be deposited before the poly-siloxane bank structure is formed. The method further may include forming one or more insulating strips on the poly-siloxane bank structure, for example, between apertures. At least one insulating strip may include an overhanging portion or a base portion or both, either or both of which may be formed of poly-siloxane in whole or part.
In another implementation, an organic light-emitting device (OLED) may include a plurality of light-emitting elements, each light-emitting element comprising an electro-luminescent material disposed between electrode elements, and at least one structure comprising poly-siloxane material, wherein the structure is configured to separate elements of the OLED. The at least one structure may be a poly-siloxane bank structure configured to separate light-emitting elements from each other, and may include apertures into which light-emitting elements are arranged. The poly-siloxane bank structure may physically and electrically insulate the light-emitting elements from each other. The OLED further may include one or more insulating strips configured to separate electrode elements of the OLED. The at least one insulating strip may include an overhanging portion or a base portion or both, either or both of which may be formed of poly-siloxane in whole or part. Alternatively, the at least one structure may be one or more insulating strips configured to separate electrode elements of the OLED. The at least one insulating strip may insulate neighboring electrode elements from each other.
One or more of the following advantages may be provided. The use of a poly-siloxane insulating structure may result in lower manufacturing cost since poly-siloxane can be processed from solution. Moreover, in forming the insulating structures, poly-siloxane may be directly patterned using photo-lithographic techniques, which may reduce cost, time and the number of flaws introduced in manufacturing as compared to indirect photo-patterning processes. The resulting poly-siloxane insulating structures may retain less of harmful reactive chemicals or water than the processing of insulating structures made of other materials, so that the reliability and lifetime of the OLED may be improved. Because poly-siloxane exhibits non-wetting behavior with respect to many solutions that are used to deposit organic materials in the OLED, the use of poly-siloxane as a structure-defining material may help contain other fabrication materials in their desired locations within the OLED and thus prevent undesirable electrical bridging and other manufacturing flaws. Furthermore, poly-siloxane can be cured at temperatures that are compatible with other materials used in the OLED, thus avoiding damage to the OLED components.
Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.